Structural Characteristics And Stability Evaluation Of Lower Slice Roof Under The Bifurcation Coal Seam

Bifurcation coal seam is a kind of coal seam with short distance,which is common in the area of Huaihe River and Huaihe River.Due to the limitation of coal mining technology,it cannot be mined in one time.Mining upper stratified coal will destroy the integrity of lower stratified coal roof,which is easy to fall and collapse,seriously affecting the safety production.Therefore,it is very necessary to study the evolution process and stability of the lower layer roof structure.Taking No.7 coal seam in Xutuan coal mine as the research object,on the basis of systematic collection of mine geology and other related data,this paper analyzed the sedimentary characteristics of No.7 coal seam by using the methods of geological statistics and theoretical analysis,and divided the types of strata combination;used theoretical calculation,numerical simulation and field exploration methods to study the roof and floor mining damage characteristics of No.71 coal seam in upper slicing,and analyzes the lower slicing No.72 coal roof rock structure mining evolution process,and the stability of the regenerated roof was evaluated,which provided a scientific basis for the roof treatment and management of the working face.The main achievements and understandings are as follows:1.Based on the analysis of sedimentary environment of Xutuan coal mine,the reasons of No.7 coal seam bifurcation phenomenon were discussed;according to the lithology,thickness,structural characteristics and other indicators,the structure type and lithology type of No.7 coal seam roof and floor were divided,the results showed that the lithology of 7 coal seam roof and floor were mainly soft rock,followed by medium hard rock;the influence of structural development characteristics of 7 coal seam on coal seam recovery was analyzed.2.The roof and floor structure characteristics of No.7 coal seam were analyzed.The failure depth of the coal roof and floor in the upper layer No.71 coal were calculated by the theoretical formula.Five types of structure were established according to the interval of bifurcation coal seam,and the mining failure characteristics of No.71 coal seam with different structure types were studied by FLAC3D numerical simulation method,and the results were compared with the drilling exploration results.3.Based on the analysis of mining damage degree of No.71 coal roof and floor,according to the relationship between the thickness of floor and the damage degree,the No.72 coal regenerated roof was divided into three types:Ⅰ type、Ⅱ type、Ⅲ type.The regenerated roof of 72210 working face is mainly Ⅱ type.4.The numerical simulation method was used to study the roof failure characteristics of layered No.72 coal mining under the condition of regenerated roof,and the simulation results of mining No.71 coal and No.72 coal under the condition of primary roof were compared.The stability of regenerated roof of lower layered No.72 coal was evaluated,and the instability of regenerated roof was revealed.Figure[45]Table[12]Reference[112]...